Industrial truck with load supporting members for handling a plurality of stacked articles



June 8, 1965 w, s, MlLLER 3,187,917

INDUSTRIAL TRUCK WITH LOAD SUPPORTING MEMBERS FOR HANDLING A PLURALITY 0F STAGKED ARTICLES Filed Jan. 15, 1962 3 Sheets-Sheet l ae WENDELL 5. MILLER IN VEN TOR ATTDRHEY June 8, 1965 w. s. MILLER 3,187,917 INDUSTRIAL TRUCK WITH LOAD SUPPORTING MEMBERS FOR HANDLING A PLURALITY 0F STAGKED ARTICLES Filed Jan. 15, 1962 Z5 Sheets-Sheet 2 7 a I v 1 g 4?.

WENDELL s. MILLE? INVENTOR.

ATTOEN EV June. 8, 1965 w. s. MILLER 3,337,917

INDUSTRIAL TRUCK WITH LOAD SUPPORTING MEMBERS FOR HANDLING A PLURALITY OF STACKED ARTICLES WENDELL 5. 14114.62 iii T19 INVENTOR- ATToIZHEY letized cartons.

United States Patent O INDUSTRIAL TRUCK WITH LOAD SUPPORTING MEMBERS FOR HANDLING A PLURALITY F STACKED ARTICLES Wendell S. Miller, 1341 Comstock Ave., Los Angeles, Calif. Filed Jan. 15, 1962, Ser. No. 166,135 Claims. (Cl. 214-730) This invention relates to an improved truck for handling and moving work pieces, such as boxes of merchandise in a warehouseor the like. i

There have heretofore been devised various different types of fork-lift trucks having fork portions adapted to be received beneath a work piece or stack of work pieces, and carry them from place to place in a warehouse. to provide an improved truck of this general type which is able to remove from a stack of work pieces (or insert in sucha stack) a single item or series ofitems located beneath the top of the stack. Conventional trucks are not adapted to remove or insert such intermediate or lower items from a stack, but instead must always remove or replace only an upper work piece or upper group of work pieces. As will be apparent, there are obviously many situations in which it may be desirable to handle selectively one of. the lower units, in a stack, as for instance where a lower box contains a particular type, size or color of merchandise which is wanted.

The above discussed object is attained by providing the truck with two separate work supportingtforks or similar work supporting structures, which structures are adapted to support respectively two different work pieces in a stack. These supporting structures may take the form of two vertically spaced forks projecting horizontally, and adapted to project into and engage in support The general object of the present invention is ing relation two box holding pallets in a stack of pal- Thefupper of the two forks or work supporting structures may then hold a top box or top group 'of boxes, while the lower work supporting structure removes from the stack ,a lower box, or group of boxes. After such removal, the top work supporting structure may lower the upper boxes onto the remaining portion of the stack, and then bewithdrawn from engagement with the coacting pallet, so that the ultimate overall result is the desired removal'of a lower box or boxes from the stack. 7

To' achieve the discussed type of operation, the two ,forks or work supporting structures are mounted for appropriate movementrelative to one another or relative to the truck frame. Preferably, each of the two structures is movable vertically relative to the other structure, and

relative to the frame,and at. least one of the structures I is mounted for horizontal retracting movement, to withdraw the lower box or work piecehorizontally from its original position in the stack (or.to insert it in the stack if desired). The horizontallyretractable work supporting structure maybe mounted for its dualtype of movement by mounting it for horizontal movement on and relative the control apparatus may be capable, 'during a box re-' "moving cycle, of first automatically moving the two forks upwardly in unison through a short distance, to simultaneously lift all of the boxes or workpieces located above a predetermined point in a stack, and then autoand project forwardly in a horizontal condition.

Patented June 8, 1965 matically shifting to an altered condition in which the lower fork is stopped but the upper fork continues its upward movement, so that the box or boxes supported by the lower fork are out of engagement with the upper a fork and are therefore free for lateral or horizontal removal from the stack.

The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiment illustrated in the accompanying drawings, in which:

FIG. 1 is a side view of a fork lift truck constructed in accordance with the invention; 7

FIG. 2 is a plan view of the FIG. 1 truck;

FIG. 3 is a front view of the truck of FIGS. 1 and 2, taken on line 3--3 of FIG. 1;

FIG. 4 is a representation of the control mechanism and circuit of the truck;

FIG. 5 is an enlarged fragmentary vertical section taken on line 5-5 of FIG. 2;

FIG. 6 is a further enlarged horizontal section taken on line 66 of FIG. 5; and

FIGS. 7, 8 and 9 are side views representing the apparatus in three different load handling conditions.

With reference first to FIGS. 1, 2 and 3, it is noted that there is shown at 10 in these figures a vehicle having a body or frame structure represented at 11, mounted by wheels 12 for movement along a fioor or support surface 13. The vehicle is driven along surface 13 by a main engine or motor, typically located Within a rear portion 14 of the housing, with the front wheels 12 adapted to be turned to steer the vehicle by means of a steering wheel 15 actuable by a driver positioned within a drivers seat 16.

The vehicle 10 carries at its forward side a forwardly projecting typically horizontal base member 17, which movably mounts two forwardly projecting work supporting forks 18 and 19. While thearrangement particularly illustrated in the drawings contemplates typically that the work supporting mechanism is mounted at the front end of the vehicle, it will of course be understood that, if desired, similar mechanism may be carried at or project from a side of the vehicle or its rear, if such positioning would facilitate the operation of the apparatus for a particular use. i -In the arrangement illustrated, the platform or base 17 is rigidly secured at its rear end 20 to the front of the vehicle frame 11, to be held in fixed relation thereto, This base 17 is rigid, and may typically be formed of sheet metal, suitably reinforced internally to attain sufiicient strength. 'At a location nearthe center of platform 17, there is mounted to this platform a hydraulically .actuated piston and cylinder mechanism 24 for actuating a carrier part 25 upwardly and downwardly relative to platform 17. In order to increase the range of vertical movement of carrier part 25, the piston and cylinder mechanism 24 may be of .a telescopic type, having a piston 26 (see FIG. 7) which is connected to the underside of carrier part 25, and which is actuated .by the introduction of fluid pressure into a composite cylinder formed of several telescopic sections 27. As will be apparent, the introduction of pressure fluid into the lower end of the bottom cylinder section 27, through a line 28, causes. the various sections 27 to progressively extend upwardly, and to actuate piston 26 upwardly.

The carrier part 25 may take the form of a generally horizontal framework, disposed essentiallyparallel to but spaced upwardly above 'bottom platform '17, with the framework of part 25 desirably consisting of a transverse horizontal element 28' carrying twoparallel track elements 29 extending in afront-to-rear direction with to engage fork 19 with'a Work piece.

a, Q3 respect to vehicle 10. At their rear ends, tracks 29 carry an upwardly projecting wall or structure 39, which may Q der mechanism 24.

The work supporting fork structure 19 may consist of two parallel forwardly projecting horizontal rigid arms 32, having upper horizontal surfaces on which a rectangular box or other work unit may be supported, and having forward tapered portions 33 to facilitate engagement of the arms 32 with the work unit. Structure 19 is mounted for front-to-rear movement relative to vehicle and relative to carrier part 25, by providing the two arms or portions 32 of fork 19 with rollers 34, engageable with tracks 29. The resulting movement of fork 19 along tracks 29 is in a directly horizontal plane, This fork has at its rear end an upwardly projecting vertical wall 35, to which there may be attached two horizontally extending cylinders 36, containing pistons having piston rods 37 attached rigidly to upstanding wall 3! of carrier part 25. The axes 38 of the piston and cylinder mechanism 36, 37 extend in a horizontal front-to-rear direction,

ders 36, fork 19 may be actuated forwardly and rearwardly relative to carrier part 25.

The second and upper work supporting fork 16 may i be constructedessentially the same as fork 19, having two forwardly projecting parallel arms or portions 40 shaped'in correspondence with arms 32' of fork 19, and connected at their rear ends to a vertically extending may be cylindrical, except as that surface is interrupted to provide a toothed vertical rack 43 at one side of the column, and a vertical guideway recess or slot 44 (FIG. 6) at the diametrically opposite side of the column.

About column 42, there is slidably received a rigid cylindrical sleeve 45, which is a close fit on the external cylindrical surface 46 of column 42, and'is therefore 1 guided by the column for vertical movement relative thereto. The previously mentioned rear wall 41 of upper fork 18 is rigidly welded or otherwise attached to sleeve 45, to actuate the fork 18 in accordance with upward and downward movement of. sleeve 45. Pivotal movement of the fork structure about the vertical axis 47 of column 42 is prevented by providing sleeve with one or more keys or lugs 48 (FIGS'S and 6) which are received within guideway 44 in a'manner' keying the sleeve 45 against rotary movement while permitting vertical movement of the sleeve.

The fork 18 ispower actuated upwardly and downwardly by means of a fluid operated rotary 'motor 49,

suitably mounted to sleeve 45, and driving a gear 56 which projects through an aperture 51 in sleeve 45 (see FIG. 5) to engage rack teeth 43 on column 42, and therefore move sleeve 45and fork 18 upwardly and downwardly in correspondence .with the supply of pressure fluid to motor 49. The motor 49 is desirably of a positive displacement liquid actuated Ltype, so that the extent of upward or downward movement of fork 18 7 'fork structure.

including an off position in which no fluid passes there- I may be exactly predetermined for a predetermined amount of fluid flow through motor 49.

ing motors 24, 36 and 49 by means of a pump represented at 52, which pump may becontinuously driven by the main engine 153 for propelling the truck. Pump 52 may take its suction from a reservoir 53 to which fluid returning from the various motors is conducted. The high pressure liquid from pump 52 is taken to a control unit 54 having manually actuated control arms or handles 55, 56, 57 and 58 which are adjacent the drivers seat 16, to be accessible for manual actuation by the driver of the vehicle. Pump 52 may also have a bypass line 59 leading from its discharge side to its suction side, and containing a pressure release valve 60 acting to permit the output fluid from the pump to bypass back to the suction side of the pump in the event of development of an excessive pressure, as when unit 54 is in a condition closing off thedelivery of the pressure liquid to all of'the various fluid motors 24, 36 and 49.

FIG. 4 represents somewhat diagrammatically a typical valve arrangement for controlling thefiow of fluid within "control unit 54. This illustrated arrangement includes four valves 61, 62, 63 and 64, which are actuable between different settings by the four previously mentionedhandles 55, 56, 57 and 58 respectively. A first of the valves, number 61, is provided for the purpose of shifting the control mechanism between a predetermined automatic condition, and a manually controlled condition. In the first of its settings, the non-automatic setting, valve 61 connects the discharge and suction lines 65 and 66 of the pump and reservoir circuit to a pair of lines 67 and 68 respectively, which are in turn connected to valves 62, 63 and 64, in parallel. When valve 61 is in its second setting, the automatic setting, valve 61 connects lines 65 and 66 to a second pair of lines 69 and 70, respectively. Line 69 has two branches 69 and 69", leading'pressure fluid to fluid motor 49 and elevating cylinder 24, while line 70 is a return line through which fluid from motor 49 returns to valve 61, to pass through that valve into line66 leading back to reservoir. 53. Connected into line 69 thereis apreferably normally open solenoid valve 71, which when electrically energized 'by a circuit to be discussed at a later point acts to close line 69", and prevent, the admission of. further pressure an off position, an elevating position in which lines 67 and 68 are connected through valve 63 to lines 69' and 76 in a manner causing motor 49'to elevate sleeve 45 and fork 18, and areversed position in which valve 63 connects the motor reversely' tolines 67 and 68, to cause the motor to lower sleeve 45and the connected Similarly, valve has three positions,

through, a second setting in which valve 64 connects lines 67 and 68 to a pair of lines 73 and 74 leading to cylinder 36 in'a manner causing forward movement of fork 19, andia third setting in which the connections to lines 73 'and 74' are reversed to cause rearward movement of fork 19. a I V Solenoid valve 71 is energized to its closed position by current from a power source represented as a battery 75 in FIG. 4, and-under the control of a'micro-switch 76 carried by sleeve 45. Referring particularly to FIGS.

5 and 6, this micro-switch 76 may be carried by a vertical plate 77 which is, typically welded to and projects outwardly from sleeve 45. Switch 76 has a wire feeler or finger 77', adapted to swing about an axis 78 (FIG. 6),

and actuated by a cam 79 typically having'the crosssection represented in FIG. 5. More particularly, this cam may have a reduced diameter portion 80 which is normally opposite finger 77' of the micro-switch, so that the finger normally remains in the full line position of FIG. 5. This reduced diameter portion 80 may continue about most of the circular extent of the cam, so that finger 77' remains in the full line open switch position of FIG. 5 until cam 79 turns through almost a complete revolution, in a clockwise direction as viewed in FIG. 5, with the switch ultimately being actuated to the broken line closed switch position near the end of a revolution, by engagement of peak portion 81 of the cam with finger 77 of the micro-switch.

Cam 79 is mounted rotatably about a shaft or pin 82, which is rigidly secured to plate 77, and is keyed against rotation relative thereto. There is also mounted about shaft 82 a gear 83 which projects through an aperture 84 in the side of sleeve 45 into engagement with rack teeth 43. Thus, gear 83 turns freely about shaft 82 in correspondence with upward and downward movement of sleeve 45.

Cam 79is yieldingly urged to the position of FIG. 5 by a coil spring 185 connected at its opposite ends to shaft 82 and the cam, and is rotatable against the tendency of this spring in a clockwise direction by gear 83. A clutch mechanism is provided between gear 83 and cam 79, typically taking the form of a magnetic clutch including an annular electromagnet 85 secured to plate 77. Gear 83 may be of a magnetic material such as iron, so that the magnetic field from electromagnet 85 is transmitted through gear 83, and acts to pull cam 79 (which is also formed of iron or other magnetic material) into engagement with gear 83. The cam 79 is normally returned axially by spring 185, with the spring acting to yieldingly resist the magnetically controlled axial movement of cam 79 into engagement with gear 83. When coil 85 is energized, and cam 79 is in engagement with gear 83, the cam is magnetically clutched to the gear to turn with the gear about shaft 82. As soon as the circuit to electromagneticcoil 85 is broken, however, spring 185 returns cam 79 rotatively to its FIG. 5 position, and axially to its FIG. 6 full line position.

Electromagnet 85 is energized by a suitable power source, represented as a battery 86 in FIG. 4, under the control of a series connected switch 87, which is actuable to closed condition by movement of lever 55 forwardly to the setting in which lines 65 and 66 are connected to lines 69'and 70, respectively.

In addition to the above discussed micro-switch 76, sleeve 45 carries also a second micro-switch 88, which is actuable by a mechanism which is a duplicate of the cam 79, gear 83, spring 185, electromagnetic clutch ele- I ment 85, and other associated parts illustrated in FIGS.

5 and'6 in connection with the first mentioned microfork-lift truck, reference is first made to FIG. 7, which illustrates a stack of boxes 90, each of which is resting on a pallet 91 having a recess or recesses into which the .forks 18 and 19 are adapted to project in a relation for supporting the boxes by means of the forks. Assume in FIG. 7 that it is desired to remove the next to top box 90' from the stack, leaving the three lower boxes and the uppermost box 90" in the stack. As a first step, the op- ,erator drives the truck 10 toward the stack of boxes, preferably to a position in which the two forks 18 and 19 are almost but not quite in engagement with the box stack (say for example to the position illustrated in FIG. 1).

It may be assumed that fork 19 is already in its forwardly advanced position, in which it projects forwardly approximately the same distance as does fork 18. It may also be assumed that valve handle 55 of control unit 54 is in its rearwardly actuated nonautomatic position, in which lines 65 and 66 are connected to lines 67 and 68, and not to lines 69 and 70. This enables the operator to control movement of forks 18 and 19 manually by the other three valves 62, 63, and 64. After the truck has been driven to a position in which forks 18 and 19 are closely adjacent the stack of boxes, the driver actuates valves 62 and 63 to move the forks to the elevations illustrated in FIG. 7, that is, to a position in which bottom fork 19 is opposite the pallet which supports box 90', while the upper fork 18 is opposite the pallet which supports top box 90". The vertical movement of fork 19 to its desired position is caused by admitting fluid to line 72 and cylinder 24, or withdrawing fluid from this line and cylinder by appropriate setting of valve 62, to cause cylinder 24 and its attached piston to move carrier part 25 and fork 19 upwardly or downwardly to a proper position. Similarly, valve 57 is actuated to control the direction of flow of pressure fluid to motor 49, until that motor has lowered or raised fork 18 to a proper setting, at which time valve 63 is placed in its olf position to lock fork 18 at the proper elevation.

After the forks are in their desired vertical settings, the truck is driven forwardly to the FIG. 7 position, so that the two forks are received within and engage the pallets beneath the upper two boxes 90' and 90". The operator at this juncture may then shift handle 55 forwardly, to turn valve 61 to its automatic setting, in which lines 65 and 66 are now connected to lines 69 and 70 respectively, rather than to lines 67 and 68. This forward movement of handle 55 also actuates switch 87, to energize electromagnets and 85', and thereby magnetically clutch together the cam 79 and gear 83 (FIGS. 5 and 6) associated with each of the two micro-switches 76 and 88. Prior to such energization of the electromagnets, gears 83 associated with these two electromagncts were of course free to rotate upon upward or downward movement of sleeve 45, without having any effect on either of the earns 79.

Immediately upon forward movement of valve handle 55, lines 69' and 69" commence to admit pressure fluid from pump 52 to motor 49 and cylinder 24, to move both of the forks 18 and 19. upwardly. The motor 49, and cylinder 24, as well as other portions of the fluid system, are all predesigned to cause the two forks to move upwardly exactly in unison, when valve handle 55 is actuated forwardly as discussed above. The upward movement of fork 18 rotates the two gears 83 associated with micro-switches 76 and 88, and since cams 79 are clutched to these gears, the cams are correspondingly turned against the tendency of their springs 185. After the two forks 18 and 19 have moved upwardly through a predetermined, short distance, say to the point at which bottom fork 19 reaches the elevation shown in FIG. 7, microswitch 76 is automatically actuated by engagement with the peak portion 81 of cam 79, to close theelectrical circuit to solenoid valve 71, which valve in turn closes the line 69" to cylinder 24, to prevent the flow of any further fluid to or from cylinder 24. Thus, the lower fork 19 is locked in this slightly elevated position (see FIG. 8). The gear 83 which is associated with the second microswitch 88 may be of a larger diameter than is the gear associated with micro-switch 76, or the cams may be different, with these parts being predetermined in a relation such that micro-switch 88 is not closed until sleeve 45 and fork 18 have moved upwardly a substantial distance beyond the point at which switch 76 is closed, preferably through a distance twice as great as that required to actuate switch 76. Thus, sleeve 45 and fork 18 continue upwardly after fork 19 has stopped, and until fork 18 reaches a position such as that shown in FIG. 8, in which discussed process.

the upper box 94)" and its pallet are-spaced substantially above intermediate box 90'. At this FIG. 8 position, micro-switch 88 is actuated, to close the circuit to solenoid 89, which pulls handle 55 rearwardlly to shift valve 61 to itsmanually controlled non-automatic condition in which lines 65 and 66 are again connected to lines 67 and 68. Since all the valves 62, 63 and 64 were of course shifted to closed or off positions prior to actuation of valve 61 to its automatic setting, the return of valve 61 and handles 55 to their non-automatic condition completely stops all motionof the boxes and forks. The operator may then actuate valve 64 to cause cylinders 36 to move fork 19 and its carried box 90' leftwardly, as to the broken line position of FIG. 8, so that the desired intermediate box 90' is now removed from the stack. The operator may next turn Valve 62 to'a position for withdrawing fluid from cylinder 24, to thereby lower carrier part 25, fork 19, and

the removed box 96' to the FIG. 9 readily accessible position; and may actuate valve 63 to cause motor 49 to move sleeve 45 and fork 18 downwardly to the FIG. 9 setting in which the top box 90" and its pallet again rest on the stack. After the apparatus has reached the FIG. 9 conditron, the operator backs the. truck leftwardly as viewed in FIG. 9, to withdraw fork 18 from its engaged pallet, and leave the stack in its original condition except that the next to top box has been removed. It will of course be apparent that anybox or work piece may be removed from the stack in the manner discussed above, or a Work piece may be inserted in the stack at an intermediate or lower location by a manually controlled reversal of the I claim:

1. A truck for lifting work pieces arranged in a Stack, said truck comprising a wheeled vehicle frame, two load supporting structures movably carried by said frame and projecting to positions for supporting respectively two different upper and lower work pieces in said stack, first power operated means for moving a first of said structures and 21 carried work piece upwardly and downwardly relative to said frame, a carrier structure, second power operated means for actuating said carrier structure upwardly and downwardly relative to the frame, means mounting a second of said load supporting structures to said carrier part for upward and downward movement therewith,

means for actuatingsaid second load supporting structure horizontally relative to said carrier structure between a position generally beneath said first load supporting structure and a horizontally retracted position, and automatic control means operable through a predetermined cycle of operation causing said first and second power operated means to first move said carrier structure and both of said load supporting structures upwardly in unison through a limited'distance and then halt the upward movementof said carrier structure and said second load supporting structure while continuing the upward movement of said first load supporting structure.

2. A truck for lifting work pieces arranged ina stack as recited in claim 1, in which said automatic control means include a first electric switch responsive to upward movement of said load supporting structures in unison through said limited distance, means operable by said switch upon actuation thereof to halt said upward movement of said carrier structure, a second switch responsive to continued'upward movement of said first load supporting structure through a predetermined distance, and means operable by said second switch upon actuation thereof to v 'projecting'to positions for supporting respectively two different upper and lower work pieces in said'stack, first power operated means for moving a first of said structures and it carried work piece upwardly and downwardly relative to said frame, a carrier structure, second power operated means for actuating said carrier structure upwardly and downwardly relative to the frame, means mounting a second of said load sup-porting structures to said carrier part for upward'and downward movement therewith, means for actuating said second load supporting structure horizontally relative to said carrier structure between a position generally beneath said first load supporting structure and a horizontally retracted position, control means for said first and second power actuated means actuable between a manually controlled condition and an automatic condition, said control means including automatic control means operable in said automatic condition through a predetermined cycle of operation causing said first and second power operated means to first move said carrier structure and both of said load supporting structures upwardly in unison through a limited distance, and then halt the upward movement of said carrier structure and said second load supporting structure while continuing the upward movement of said first load supporting structure.

4. A truck'for lifting work pieces arranged in a stack as recited in claim 3, in which said automatic control means include a first electric switch responsive to upward movement of said load supporting structures in unison through said limited distance, means operable by said switch upon actuation thereof to halt said upward movement of said carrier structure, a second switch responsive to continued upward movement of said first load supporting structure through a predetermined distance, and means operable by said second switch upon actuation thereof to halt said continued upward movement of said first load supporting structure.

5. A truck for lifting work pieces arranged in a stack, said truck comprising awheeled vehicle frame, an engine forpropelling said wheeled frame along a floor surface, two-load supporting fork structures movably carried by said frame and projecting to vertically spaced ositions for supporting respectively two different upper and lower work pieces in said stack, fluid pressure actuated means for moving a first of said fork structures and a carried work piece upwardly and downwardly relative to said frame, a carrier structure, fluid pressure actuated means for actuating said carrier structure upwardly and downwardly relative to the frame, means mounting a second of said load supporting structures to said carrier structure for upward and downward movement therewith and horizontal movement relative thereto, fluid pressure actuated means for actuating said second load supporting fork structure horizontally relative to said carrier structure between a position generally beneath said first load supporting fork structure and a horizontally retracted position, a control system including valves operable to manually control said three fluid pressure actuated means, said control system including a control valve operable to shift said system between a manual condition and an automatic condition and operable in the latter. condition to admit fluid to both of said two first mentioned fluid pressure actuated means, to thereby move both fork structures upwardly in unison, two switches operable in sequence upon upward movement of said first fork structure, a valve operable by a first of said switches to close off the flow of pressure fluid to said second mentioned fluid pressure actuated means, and means operable by said second switch to actuate said control valve from said automatic condition to said manual condition.

6. A truck for lifting work pieces arranged in a stack, said truck comprising a wheeled vehicle frame, twoupper and-lower load supporting structures both carried movably by said frame and projecting generally horizontally to positions for supporting respectively two dilferent upper and lower work pieces in said stack, means for shifting said lower load supporting structure generally horizontal- 1y relative to said upper load supporting structure, with said lower work piece supported on said lower structure and said upper workpiece supported independently on said upper structure, and between an active position in which said lower structure and work piece are generally beneath said upper structure and a retracted position in which said lower structure is withdrawn horizontally from beneath the upper structure, and power operated means for actuating both of said load supporting structures upwardly and downwardly relative to said frame and one relative to the other, said last mentioned means including means operable to move said upper load supporting structure, with said upper work piece supported thereon, gen erally vertically when said lower load supporting structure is in said active position and also when it is in said retracted position.

7. A truck for lifting work pieces arranged in a stack, said truck comprising a wheeled vehicle frame, two upper and lower load supporting structures both carried movably by said frame and projecting generally horizontally to positions for supporting respectively two ditlerent upper and lower work pieces in said stack, a carrier structure mounted to said frame for essentially vertical movement and movably carrying said lower load supporting structure, means for shifting saidlower load supporting structure generally horizontally relative to said carrier structure and said upper supporting structure, with said upper and lower work pieces supported by said two supporting structures respectively, and between an active position in which said lower structure and work piece are generally beneath said upper structure and a retracted position in which said lower structure is withdrawn horizontally from beneath said upper structure, means for actuating said carrier part and thereby said carried lower supporting structure upwardly and downwardly relative to said frame, and power actuated means for moving said upper load supporting structure, with said upper work piece supported thereon, generally vertically when said lower load supporting structure is in said active position and also when it is in said retracted position.

8. A truck as recited in claim 7, in which said last mentioned means are operable to move said upper load supporting structure generally vertically relative to said lower load supporting structure in both of said active and retracted positions. I

9. A truck for lifting work pieces arranged in a stack, said truck comprising a wheeled vehicle frame, two upper and lower load supporting structures both carried movably by said frame and projecting generally horizontally to positions for supporting respectively two different upper and lower work pieces in said stack, a carrier structure mounted to said frame for essentially vertical movement and movably carrying said lower load supporting structure, power actuated motor means for shifting said lower load supporting structure generally horizontally relative to said,

carrier structure and said upper supporting structure, with said upper and lower work pieces supported by said two 10 supporting structures respectively, and between an active position in which said lower structure and work piece are generally beneath said upper structure and a retracted position in which said lower structure is withdr'awn'horizontally from beneath said upper structure, second powfer actuated motor means for actuating said carrier part and thereby said carried lower'supporting structure upwardly and downwardly relative to said frame, and third power actuated motor means for moving said upper load supporting structure, with said upper work piece supported thereon, generally vertically relative to said frame and relative to said lower load supporting structure when said lower load supporting structure is in said active position and also when it is in said retracted position.

10. A truck for lifting work pieces arranged in a stack, said truck comprising a wheeled vehicle frame, two load supporting structures both carried movably by said frame and projecting to positions for supporting respectively two different upper and lower work pieces in said stack, power operated drives for actuating said two structures respectively generally vertically relative to the frame and operable to move said structures generally vertically relative to one another, and automatic control means for said drives operable through a predetermined cycle of operation to first actuate both drives to move said two structures and carried Work pieces upwardly in unison, and to then automatically advance an upper one of said structures and said upper work piece upwardly farther relative to the other structure and lower work piece, said automatic control means including a first control element responsive to limited upward movement of said two structures in unison through a predetermined distance to halt the upward movement of said lower structure after said limited movement while continuing the upward movement of said upper structure, and a second control element responsive to said continued upward movement of said upper structure to halt that movement after a predetermined travel.

References Cited by the Examiner UNITED STATES PATENTS 1,149,309 8/15 Von Phul 221-134 1,149,310 8/ 15 Von Phul 221-134 2,496,399 2/50 Lesser 214-1642 X 2,624,470 1/53 Geist 214-1642 X 2,699,697 1/55 Kelso 214-650 X 2,983,391 5/61 Insolio et a1 214-670 X 3,045,850 6/62 Carr et al 214-620 FOREIGN PATENTS 165,993 11/55 Australia.

1,094,190 12/60 Germany.

HUGO O. SCHULZ, Primary Examiner.

ERNEST A. FALLER, JR., Examiner. 

6. A TRUCK FOR LIFTING WORK PIECES ARRANGED IN A STACK, SAID TRUCK COMPRISING A WHEELED VEHICLE FRAME, TWO UPPER AND LOWER LOAD SUPPORTING STRUCTURES BOTH CARRIED MOVABLY BY SAID FRAME AND PROJECTING GENERALLY HORIZONTALLY TO POSITIONS FOR SUPPORTING RESPECTIVELY TWO DIFFERENT UPPER AND LOWER WORK PIECES IN SAID STACK, MEANS FOR SHIFTING SAID LOWER LOAD SUPPORTING STRUCTURE GENERALLY HORIZONTALLY RELATIVE TO SAID UPPER LOAD SUPPORTING STRUCTURE, WITH SAID LOWER WORK PIECE SUPPORTED ON SAID LOWER STRUCTURE AND SAID UPPER WORKPIECE SUPPORTED INDEPENDENTLY ON SAID UPPER STRUCTURE, AND BETWEEN AN ACTIVE POSITION IN WHICH SAID LOWER STRUCTURE AND WORK PIECE ARE GENERALLY BENEATH SAID UPPER STRUCTURE AND A RETRACTED POSITION IN WHICH SAID LOWER STRUCTURE IS WITHDRAWN HORIZONTALLY FROM BENEATH THE UPPER STRUCTURE, AND POWER OPERATED MEANS FOR ACTUATING BOTH OF SAID LOAD SUPPORTING STRUCTURES UP- 